"The fact that North Korea proposed talks (with the U.S.) ahead of the South Korea-China summit signifies its intent to keep China in check," said Kim Yong-hyun, a professor of North Korean studies of Dongguk University in Seoul, South Korea.

I suspect they mean keeping the initiative on Korean Peninsula negotiations in Korean hands rather than Chinese ones - that would fit with this suggestion, pre-empting anything the US might do as well as the PRC.